Improvement in stove-pipe elbows



2 Sheets-Sheetl'. F. HOE LTGE.

STOVE-PIPE ELBOW'S. 1 3 9z5 Patented Oct. 31, 1876.

Fly. 1

. WITNESSES INVENTOR 6% fllfln'lu'l x UNITED STATES PATENT QFFICE.

FREDERICK HOELTGE, OF CINCINNATI, OHIO, ASSIGNOR TO AUGUSTUS HOELTGE, OFSAME PLACE.

IMPROVEMENT IN STOVE-PIPE ELBOWS.

Specification forming part of Letters Patent No. 183,926, dated October31, 1876; application filed September 30,1876.

To all whom it may concern Be it known that I, FREDERICK HOELTGE, ofCincinnati, in the county of Hamilton and State of Ohio, have inventedcertain new and useful Improvements in Processes and Appliances forMaking Stove Pipe and other Elbows of Sheet Metal; and I hereby declarethat the following is a full and exact description of my said invention,reference being bad to the accompanying drawings, making part of thisspecification.

My invention consists, in part, in a process of forming elbows of sheetmetal by stamping a blank in successive dies, so as to form a deepelliptical concavity in its central part, and a convexity at each sideof the said central concavity,separated therefrom by straight or nearlystraight lines, so that by bending the sides of the blank forward onthese dividinglines until their edges meet, the curved sides will becomeconcentric, or nearly so, with the middle of the blank, the latterforming the outer curve of the elbow, while the meeting sides form theinner curve.

The invention further relates to the construction of blanks and diesemployed to form elbows, as above set forth.

In the accompanying drawing, Figure 1 is a plan of the blank employed.Fig. 2 is a plan of the die in which the first stamping is performed.Fig. 3 is a plan of the pressed blank in position in the first die. Fig;4 is a transverse section on the line 4 4, Fig. 3. Fig. 5 is alongitudinal section on the line 5 5, Fig. 3. Fig. 6 is a plan or topView of the die for thesecond operation. Fig. 7 is a transverse sectionof the same on the line 7 7, Fig. 6, showing the pressed blank inposition. Fig. 8 is a longitudinal section of the same on the line 8 8,Fig. 6. Fig. 9 is a rear view of the pressed blank as it comes from thedie shown in Fig. 6, in readiness for bending into an'elbow. Fig. 10 isa perspective view of the elbow completely formed and ready forriveting.

A, Fig. 1, represents ablank, which may be cut in the form shown, out ofcommon sheetiron, or other sheet metal of uniform thickness as it comesfrom the mill. The said blank has two convex sides, a a, which form theends of the finished elbow, and two concave sides, a a which are broughttogether at the inner curve of the elbow. B is a die, the form of whichis shown in plan in Fig. 2, and in section in Figs. 4 and 5. This die isused in connection with a drop or a drawing press, in either way wellknown to those skilled in the art of stampingsheet metal. 0 is a seconddie, for imparting to the dishshaped blank A coming from the die B,three parallel concavities. A represents the blank as it comes from thedie 0, a being the central concavity therein, and a curved sides adaptedto be bent into positions concentric with the central concavity a beingseparated therefrom by straight lines at 2 2. A Fig. 10, represents theelbow completely formed and ready for joining at its edges by riveting-or other means.

Operation: The blank A, Fig. l, is placed over the die B, Fig. 2, and isforced therein by means of a draw-press operated by screw, cam,hydraulic, or other power, in customary manner; or, if the operation isto be performed by a drop-press, the blank is brought to the form shownin Figs. 3, 4, and 5 by successive stampings in dies of graduated depthand shape, on the principle well known to those skilled in the art ofstamping sheet metal. The pressed blank A is then stamped by a drawingor drop press, as before, and by means of the die 0 is brought to theshape shown at A in Figs. 6, 7, 8, and 9. The sides of the blank arethen bent on the straight lines 2 2, forwardand toward each other, untilthe edges 0, a meet and the curves a a become concentric with thecentral concavity a. In applying the elbow thus formed to use, the edgesa a are lapped to any necessary extent to give the elbow the requireddiameter, and they are then joined by riveting or other means. Thelongitudinal curvature or bowl form of the concavity a adapts it to givethe required contour to the outside of the finished elbow, and byreversing the sides of the blank in the manner described the bends a?"therein are made to produce precisely the required contour of the innercurve.

By my mode of manufacture I produce from common sheet-iron of uniformthickness perfectly formed elbows, without crimping or transversecutting, and with the least possible violence to the metal. It is notgathered and stretched again at any point, but receives a moderatestretching at the part which is to form the external bend of the elbow.This stretching is rendered comparatively slightin extent by thepeculiar mode of cutting and stamping the blank. The shape of the blankis such as to involve but little waste of metal. That the lateral bendsa may be formed with less violence, I prefer to produce in the firststamping operation slight concavities at the sides of the blank wherethe lateral ridges are subsequently to be formed.

Having thus described my invention, the following is what I claim as newand desire to secure by Letters Patent:

1. The process herein described of forming sheet-metal elbows bystamping in a suitably formed blank a central concavity and two lateralridges, and bending the sides forward and toward each other, so that thebends therein will form the inner curve of the elbow, and the centralconcavity will form the outer curve.

2. The blank A, formed with two convex sides, a a, and two concav sides,a a to adapt it to be stamped and bentiuto the shape of an elbow, as setforth.

3. The successive dies B O, the former having an oblong or ellipticcavity, and the other a similar or deeper cavity, contracted at thesides by transverse ridges.

4. The final die 0, constructed, as shown, with a central longitudinalcavity and transverse ridges, flanked by diagonal depressions, adaptedto stamp a sheet-metal blank into the required shape to be bent intoelbow form, in the manner explained.

F. HOELTGE. Witnesses:

Oeuvres KNIGHT, LE BLOND BURDETT.

